Stop the bar sticking in move mode after a press-and-hold on a widget (#6943)

Bar widgets propagate their composed press-and-hold down to the center gesture
area without handing over the grab, so the gesture area started a bar move and
then received neither a release nor a cancel to end it. The move ghost stayed on
screen for the rest of the session. Ignore the gesture unless we hold the press.

Closes #6881

Co-authored-by: Claude Opus 5 <noreply@anthropic.com>
(cherry picked from commit c0a20e2e43)

shell/plugins/bar/Bar.qml

@@ -1417,6 +1417,9 @@ Item {
     }
 
     onPressAndHold: function(mouse) {
+      // A widget above us propagates its composed press-and-hold down here without
+      // ever handing over the grab, so we'd get no release or cancel to end the move.
+      if (!gestureArea.pressed) return
       startDrag(mouse.x, mouse.y)
     }